A proposed configuration of a prior art motor vehicle includes a main battery configured to supply electric power to a motor generator for driving, an auxiliary machine battery configured to supply electric power to an auxiliary machine load, a solar charging unit configured to generate electric power using sunlight, an auxiliary battery (solar battery) configured to accumulate the electric power generated by the solar charging unit, and a step-down DC-DC converter configured to step-down an electric power from the auxiliary battery and supply the stepped-down voltage to the auxiliary machine battery (as described in, for example, JP 2015-201995A). This motor vehicle is configured to control the step-down DC-DC converter such as to supply an electric power required for staring a system from the auxiliary battery to the auxiliary machine battery at the time of starting the system of the vehicle. This configuration improves the system startability of the vehicle.